Brassica species represent important crops providing a major source of cooking oil, vegetables and condiments across many countries. The species relationship of cultivated Brassicas was described by the “triangle of U” with the three amphidiploid Brassica species B. juncea (AABB, 2n=36), B. napus (AACC, 2n=38) and B. carinata (BBCC, 2n=34) formed through interspecific hybridization between the diploid Brassica species, B. rapa (AA, 2n=20), B. nigra (BB, 2n=16) and B. oleracea (CC, 2n=18). Brassicas are closely related to the model species, Arabidopsis thaliana, for which the genome sequence was determined in 2000.
Brassica species include weedy types and cultivated varieties which demonstrate broad phenotypic plasticity. This is demonstrated by differences between root vegetable crops such as turnip, leafy forms such as Chinese cabbage, and oilseed varieties.
As well as the obvious economic reasons for studying Brassica genomes, with associated improvements in vegetable and oilseed crops, they provide also provide a model to stude the effect of polyploidisation as well as extreme morphological diversity in plant species.